Method and system for a multicast service initiation in a communication system

ABSTRACT

Method and a system for multicast service notification in cellular telephone system to enable the cellular telephone systems to provide both multicast and point-to-point services are disclosed. Several embodiments describe the signaling interaction between an access network and subscriber stations belonging to a multicast group to allow the access network to properly notify the subscriber stations of a the multicast service. Such a signaling further allows the subscriber stations to recognize the multicast service notification to participate in the multicast service.

BACKGROUND

[0001] 1. Field

[0002] The present invention relates to multicast communications, in awireline or a wireless communication system. More particularly, thepresent invention relates to a system and method for a multicast serviceinitiation in such a communication system.

[0003] 2. Background

[0004] Communication systems have been developed to allow transmissionof information signals from an origination station to a physicallydistinct destination station. In transmitting an information signal fromthe origination station over a communication channel, the informationsignal is first converted into a form suitable for efficienttransmission over the communication channel. Conversion, or modulation,of the information signal involves varying a parameter of a carrier wavein accordance with the information signal in such a way that thespectrum of the resulting modulated carrier wave is confined within thecommunication channel bandwidth. At the destination station, theoriginal information signal is reconstructed from the modulated carrierwave received over the communication channel. In general, such areconstruction is achieved by using an inverse of the modulation processemployed by the origination station.

[0005] Modulation also facilitates multiple-access, i.e., simultaneoustransmission and/or reception, of several signals over a commoncommunication channel. Multiple-access communication systems ofteninclude a plurality of remote subscriber units requiring intermittentaccess of relatively short duration rather than continuous access to thecommon communication channel. Several multiple-access techniques areknown in the art, such as time division multiple-access (TDMA), andfrequency division multiple-access (FDMA). Another type of amultiple-access technique is a code division multiple-access (CDMA)spread spectrum system that conforms to the “TIA/EIA/IS-95 MobileStation-Base Station Compatibility Standard for DualMode Wide-BandSpread Spectrum Cellular System,” hereinafter referred to as the IS-95standard. The use of CDMA techniques in a multiple-access communicationsystem is disclosed in U.S. Pat. No. 4,901,307, entitled “SPREADSPECTRUM MULTIPLE-ACCESS COMMUNICATION SYSTEM USING SATELLITE ORTERRESTRIAL REPEATERS,” and U.S. Pat. No. 5,103,459, entitled “SYSTEMAND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONESYSTEM,” both assigned to the assignee of the present invention.

[0006] A multiple-access communication system may be a wireless orwire-line and may carry voice traffic and/or data traffic. An example ofa communication system carrying both voice and data traffic is a systemin accordance with the IS-95 standard, which specifies transmittingvoice and data traffic over the communication channel. A method fortransmitting data in code channel frames of fixed size is described indetail in U.S. Pat. No. 5,504,773, entitled “METHOD AND APPARATUS FORTHE FORMATTING OF DATA FOR TRANSMISSION”, assigned to the assignee ofthe present invention. In accordance with the IS-95 standard, the datatraffic or voice traffic is partitioned into code channel frames thatare 20 milliseconds wide with data rates as high as 14.4 Kbps.Additional examples of communication systems carrying both voice anddata traffic comprise communication systems conforming to the “3rdGeneration Partnership Project” (3GPP), embodied in a set of documentsincluding Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3GTS 25.214 (the W-CDMA standard), or “TR-45.5 Physical Layer Standard forcdma2000 Spread Spectrum Systems” (the IS-2000 standard).

[0007] In a multiple-access wireless communication system,communications between users are conducted through one or more basestations. The term user refers to both animate and inanimate entities. Afirst user on one wireless subscriber station communicates to a seconduser on a second wireless subscriber station by conveying informationsignal on a reverse link to a base station. The base station receivesthe information signal and conveys the information signal on a forwardlink to the second subscriber station. If the second subscriber stationis not in the area served by the base station, the base station routsthe data to another base station, in whose service area the area thesecond subscriber station is. The second base station then conveys theinformation signal on a forward link to the second subscriber station.The forward link refers to transmission from a base station to awireless subscriber station and the reverse link refers to transmissionfrom a wireless subscriber station to a base station. Likewise, thecommunication can be conducted between a first user on a wirelesssubscriber station and a second user on a landline station. A basestation receives the data from the first user on the wireless subscriberstation on a reverse link, and routes the data through a public switchedtelephone network (PSTN) to the second user on a landline station. Inmany communication systems, e.g., IS-95, W-CDMA, IS-2000, the forwardlink and the reverse link are allocated separate frequencies.

[0008] The above described wireless communication system is an exampleof a point-to-point service, where information from the first user isintended for the second user only. In contrast, a multicast service is aservice where the information provided by a source, a user or a contentserver, is intended for a subset of all users. A model of a multicastsystem comprises a selected group of users, defined by the user's groupmembership. The group membership comprises users of subscriber stationssubscribed to a particular multicast content. For brevity, the term“member subscriber station” is used to mean “user on a subscriberstation” unless stated otherwise.

[0009] In one such a model the member subscriber stations are providedinformation with a certain content, e.g., news, movies, sports eventsand the like by one or more content servers via an assess network. Theterm access network is used herein to mean a collection of base stationsand one or more base stations' controllers. Each member subscriberstation monitors a forward link channel, over which the information isconveyed. The forward link channel may be shared among the membersubscriber stations or may be established between each member subscriberstation and the access network's station, e.g., a base station servingthe member subscriber station. Because the content server fixedlydetermines the content, the member subscriber stations are generally notcommunicating back to the access network.

[0010] Alternatively, the source of information is a user, a member ofthe selected group; the user providing information intended for theremaining members of the selected group. If the user wishes to provideinformation, the user notifies the communication system, e.g., bypressing a push-to-talk (PTT) button. Typically, the user providedinformation is routed from the subscriber station to a base station on adedicated reverse link. The base station then conveys the user providedinformation over a multicast forward link. As in case of thepoint-to-point communication system, the multicast communication systemallows both landline and wireless subscriber station to access thesystem. The above-described service is also referred to as a groupservice. Examples of group service communication systems includedispatch services, such as local police radio systems, taxicab dispatchsystems, Federal Bureau of Intelligence and Secret Service operations,and general military communication systems.

[0011] The above-mentioned multicast service communication systems aregenerally highly specialized purpose-build communication systems. Withrecent advancements in wireless cellular telephone systems there hasbeen an interest in utilizing the existing infrastructure of the (mainlypoint-to-point) cellular telephone systems for multicast services. (Asused herein, the term “cellular” systems encompasses both cellular andPCS frequencies.)

[0012] Introduction of a multicast services to cellular telephonesystems requires integration of multicast services with thepoint-to-point services provided by the current cellular telephonesystems. Specifically, both the access network and the subscriberstation need to be able support functions allowing both the multicastmode and point-to-point communication mode. Because the point-to-pointcellular telephone systems do not support multicast services, there is aneed in the art for a method and a system for a multicast serviceprocedures, specifically a multicast service initiation.

SUMMARY

[0013] Embodiments disclosed herein address the above stated needs bydetermining a multicast group identifier; and including the multicastgroup identifier in at least one periodically repeated message on afirst channel. The subscriber station monitors the periodically repeatedmessage on the channel; and decoding the periodically repeated messageto determine if a multicast service notification was included in theperiodically repeated message.

[0014] In another embodiment the above stated needs are addressed bydetermining identity of subscriber stations belonging to a multicastgroup; determining a slot of a channel in accordance with the identityof a subscriber station; and transmitting a multicast servicenotification in the slot on a channel. The subscriber station monitorsthe slot of a channel; and decodes the message conveyed in the slot todetermine if a multicast service notification was included in themessage.

[0015] In another embodiment the above stated needs are addressed byincluding an indicator into a pre-determined slot on a first channel;and including a multicast service notification into a message conveyedin a slot on a second channel, the slot corresponding to thepre-determined slot on the first channel, if a multicast servicenotification was indicated by the indicator. The subscriber stationdecodes the indicator from the pre-determined slot on the first channel;and decodes the multicast service notification in the slot on the secondchannel, the slot corresponding to the pre-determined slot on the firstchannel, if the multicast service notification was indicated by theindicator.

[0016] In another embodiment the above stated needs are addressed byincluding an indicator into a first slot on a first channel; andincluding a multicast service notification into a message conveyed in asecond slot on a second channel, the second slot corresponding to thefirst slot, if a multicast service notification was indicated by theindicator. The subscriber station decodes the indicator from the firstslot on the first channel; and decodes the multicast servicenotification in the second slot on the second channel, the second slotcorresponding to the first slot, if the multicast service notificationwas indicated by the indicator.

[0017] In another embodiment the above stated needs are addressed byestablishing a link layer protocol between a subscriber stationbelonging to a multicast group and a source of a multicast service; andconveying the multicast service notification over the link layerprotocol. The subscriber station participates in establishing the linklayer protocol; and receives the multicast service notification over thelink layer protocol.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 illustrates a conceptual block diagram of a communicationsystem capable of providing multicast services in accordance withembodiments of the present invention;

[0019]FIG. 2 illustrates a message flow in accordance with oneembodiment of notification;

[0020]FIG. 3 illustrates conceptual diagram of a page message;

[0021]FIG. 4 illustrates a message flow in accordance with anotherembodiment of notification;

[0022]FIG. 5 illustrates a relationship between signaling conveyed overa Forward Quick paging channel and signaling conveyed over a ForwardCommon Control Channel or a Forward Paging Channel in one embodiment;

[0023]FIG. 6 illustrates a message flow in accordance with anotherembodiment of notification;

[0024]FIG. 7 illustrates a relationship between signaling conveyed overa Forward Quick paging channel and a Forward Common Control Channel or aForward Paging Channel in accordance with another embodiment; and

[0025]FIG. 8 illustrates a message flow in accordance with anotherembodiment of notification;

[0026]FIG. 9 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0027]FIG. 10 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0028]FIG. 11 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0029]FIG. 12 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0030]FIG. 13 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0031]FIG. 14 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0032]FIG. 15 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0033]FIG. 16 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0034]FIG. 17 illustrates a message flow in accordance with anotherembodiment of response/channel assignment;

[0035]FIG. 18 illustrates a message flow in accordance with anotherembodiment of response/channel assignment; and

[0036]FIG. 19 illustrates a message flow in accordance with anotherembodiment of response/channel assignment.

DETAILED DESCRIPTION

[0037] Definitions

[0038] The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

[0039] The terms point-to-point communication is used herein to mean acommunication between two subscriber stations over a dedicatedcommunication channel.

[0040] The terms group service, point-to-multipoint communication,push-to-talk, or dispatch service are used herein to mean acommunication wherein a plurality of subscriber stations are receivingcommunication from—typically—one subscriber station.

[0041] The term access network is used herein to mean a collection ofbase stations (BS) and one or more base stations' controllers. Theaccess network transports data packets between multiple subscriberstations. The access network may be further connected to additionalnetworks outside the access network, such as a corporate intranet or theInternet, and may transport data packets between each access terminaland such outside networks.

[0042] The term base station is used herein to mean the hardware withwhich subscriber stations communicate. Cell refers to the hardware or ageographic coverage area, depending on the context in which the term isused. A sector is a partition of a cell. Because a sector has theattributes of a cell, the teachings described in terms of cells arereadily extended to sectors.

[0043] The term subscriber station is used herein to mean the hardwarewith which an access network communicates. A subscriber station may bemobile or stationary. A subscriber station may be any data device thatcommunicates through a wireless channel or through a wired channel, forexample using fiber optic or coaxial cables. A subscriber station mayfurther be any of a number of types of devices including but not limitedto PC card, compact flash, external or internal modem, or wireless orwireline phone. A subscriber station that is in the process ofestablishing an active traffic channel connection with a base station issaid to be in a connection setup state. A subscriber station that hasestablished an active traffic channel connection with a base station iscalled an active subscriber station, and is said to be in a trafficstate.

[0044] The term physical channel is used herein to mean a communicationroute over which a signal propagates described in terms of modulationcharacteristics and coding.

[0045] The term logical channel is used herein to mean a communicationroute within the protocol layers of either the base station or thesubscriber station.

[0046] The term communication channel/link is used herein to mean aphysical channel or a logical channel in accordance with the context.

[0047] The term reverse channel/link is used herein to mean acommunication channel/link through which the subscriber station sendssignals to the base station.

[0048] A forward channel/link is used herein to mean a communicationchannel/link through which a base station sends signals to a subscriberstation.

DETAILED DESCRIPTION

[0049] As discussed, a model of a multicast system comprises a selectedgroup of users, defined by the user's group membership. The groupmembership comprises users of subscriber stations subscribed to aparticular multicast content. One or more content servers or anotheruser provides the multicast content. FIG. 1 illustrates a conceptualdiagram of a communication system 100 capable of providing multicastservices (also referred to as a multicast call), in accordance withembodiments of the present invention.

[0050] As discussed, the multicast content may originate at a contentserver (CS). The content server may be located within the network, CS1102(1), or outside Internet (IP) 104, CS2 102(2). The content may bedelivered in a form of packets to a multicast packet data-serving node(MPDSN) 106. The term MPSDN is used because although the MPDSN may bephysically co-located or provide functionality identical to the regularPDSN (not shown), the MPSDN may be logically different from a regularPDSN. According to the packet's destination, the MPDSN 106 delivers thepackets to a packet control function (PCF) 108. The PCF is a controlentity controlling function of base stations 110 for any packet dataservices including the multicast packet data services like a basestation controller is for regular voice traffic and data trafficservices. To illustrate the connection of the high level concept of themulticast packet data services with the physical access network, FIG. 1shows that the PCF is physically co-located, but logically differentfrom a base station controller (BSC). One of ordinary skills in the artunderstands that this is for pedagogical purposes only. The BSC 108provides the packets to base stations 110. Although the term basestation is used, one of ordinary skills in the art recognizes that theembodiments are equally applicable to sectors.

[0051] Similarly, if the content originates in the CS 102(1), thecontent may be delivered to a public switched telephone network (PSTN)112. According to the content destination, the PSTN 112 delivers thecontent to base station controller BSC 108. The BSC 108 provides thecontent to base stations 110.

[0052] In yet another embodiment, the content, originating in the CS102(1) may be delivered in the form of packets via an interworkingfunction 120 to the PSTN 112. According to the content destination, thePSTN 112 delivers the content to base station controller BSC 108. TheBSC 108 provides the content to base stations 110.

[0053] The base station 110 provides the content over a forward channel114 to the member subscriber stations. As discussed, the forward channelmay be shared among the member subscriber stations or establishedbetween each member subscriber station and the base station, serving themember subscriber station. A use of a shared forward channel isdisclosed in a co-pending U.S. patent application Ser. No. 10/113,257,entitled “METHOD AND APPARATUS FOR POINT-TO-MULTIPOINT SERVICES PROVIDEDIN COMMUNICATION SYSTEMS”, filed Mar. 28, 2002. The use of common anddedicated channels for information broadcast is disclosed in aco-pending U.S. patent application Ser. No. 10/113,098, entitled “METHODAND APPARATUS FOR CHANNEL MANAGEMENT FOR POINT-TO-MULTIPOINT SERVICES INA COMMUNICATION SYSTEM”, filed Mar. 28, 2002, and assigned to theassignee of the present invention. However, one of ordinary skills inthe art understands that recited applications are for tutorial purposesonly, and other communication systems utilize channels performingsimilar function, therefore, the teaching is applicable to othercommunication systems.

[0054] Alternatively, a member subscriber station, e.g., membersubscriber station 116(1), communicates multicast content to othermember subscriber stations, e.g., a member subscriber station 116(2),via an access network. The member subscriber station 116(1),communicates the multicast content to the group over a reverse linkchannel 118, assigned to the subscriber station 116(1) by the accessnetwork. Reverse link channel assignment is well known in the art, refere.g., to the above mentioned applications Ser. Nos. 10/113,257 and10/113,098. The base station 110(1) routes the received information tothe base station 110(2), and the base station 110(2) then transmit therouted information over the forward channel 114(2) to the membersubscriber station 116(2).

[0055] When a multicast service is to be provided, a procedure enablinga multicast call commencement must be followed. Such a procedure may beseparated into several stages. During the first stage, member subscriberstations for whom the multicast service is to be provided must benotified. During the next (optional) stage, the interested membersubscriber stations respond to the notification. During the next stage,a channel over which the content will be conveyed is selected andassigned.

[0056] Notification of Multicast Call Commencement

[0057] As discussed above, when a multicast call is to be initiated, thesubscriber stations that are members of the multicast group must benotified.

[0058] In one embodiment, the access network initiates the multicastcall by broadcasting the notification information to the subscriberstations via a periodically transmitted message, e.g., an overheadmessage. The term overhead message is used herein to mean a messagepertaining to system parameters, periodically transmitted by eachsector. The overhead message, containing the multicast call notificationis transmitted by the sectors, whose coverage area contains membersubscriber stations, on a forward channel that is monitored by allsubscriber stations not engaged in another call. An example of such anarrangement in a communication system in accordance with the IS-2000standard is an overhead message transmitted on a forward paging channel(F-PCH) or a forward broadcast control channel (F-BCCH).

[0059] The multicast call is advertised by including an identifier ofthe multicast group (GROUP_ID), for whose member subscriber stations themulticast call is intended, into the overhead message. If more than onemulticast call is being initiated, the overhead message contains theidentifiers of all the multicast groups, for which the multicast callsare intended. The identifier may be sent in one overhead message;several overhead messages, or be included in all overhead messages forthe duration of the multicast call. The last option allows subscriberstations to join already pending multicast call. If the identifier isincluded in the overhead message for the duration of the multicast call,upon termination of a multicast call for a specific multicast group, thespecific multicast group identifier is removed from the message. Inaddition to the identifier, the overhead message may provide furtherinformation relevant to the advertised multicast call, e.g., the type oftraffic channel assignments, type of bearer transport used, and otherrelevant information known to one of ordinary skills in the art. Ofcourse, the remaining parts of the overhead message comprise systemrelated information as discussed above.

[0060] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 2. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2, e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art. The sectorS includes the identifier in the overhead message, which in oneembodiment comprises a broadcast system parameters messageBSPM(GROUP_IDx), and broadcasts the BSPM(GROUP_IDx) at time t₂.Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx) and take an appropriate action,e.g., start monitoring the physical channel on which the identifiedmulticast call is being transmitted, to transmit a response to theaccess network, to notify the user, and other actions in accordance withdesign of a specific communication system. FIG. 2 shows an embodiment,in which the identifier is included in the overhead message for theduration of the multicast call. Because the overhead message BSPMrepeats periodically, the identifier is, likewise, transmitted in thenext instance(s) of the overhead message BSPM. Only one instance at timet₃ is shown.

[0061] At an instant t₄, the sector S receives an indication GROUP_IDyfrom a source of information (not shown) that a multicast call intendedfor group with an identifier GROUP_IDy is to start. The sector Sincludes the identifier into the overhead message, e.g., the BSPM.Because two groups are being notified about the multicast call, thebroadcasted overhead message transmitted at an instant t₅ contains bothidentifiers BSPM(GROUP_IDx, GROUP_IDy). Subscriber station MS_3 that isa member of the group with the identifier GROUP_IDy receives theoverhead message BSPM(GROUP_IDx, GROUP_IDy), and takes an appropriateaction as described above.

[0062] At an instant t₆, the sector S receives an indication GROUP_IDxends from the source of information (not shown) that a multicast callintended for group with an identifier GROUP_IDx is to terminate. Thesector S removes the identifier from the overhead message, e.g., theBSPM, and broadcasts the overhead message, containing only theidentifier GROUP_IDy, BSPM(GROUP_IDy), at an instant t₇. Subscriberstations MS_1 and MS_2 that are members of the group with the identifierGROUP_IDx receive the overhead message BSPM(GROUP_IDy), and take anappropriate action, e.g., to terminate monitoring the physical channelon which the multicast call corresponding to the identifier GROUP_IDy isbeing transmitted. The multicast call BSPM(GROUP_IDy) is unaffected andcontinues until terminated. Upon termination, the identifier GROUP_IDyis removed from the BSPM.

[0063] Because the broadcast message is repeated periodically,subscriber stations can join the call anytime after the start of thecall. To prevent the broadcast message from affecting the paging channelcapacity, it is desirable to limit the broadcast message length.Consequently, the number of groups that may be included in the broadcastmessage is limited. Additionally, because the broadcast message changeswith each call start and termination, the subscriber stations mustmonitor every update of the broadcast message. In another embodiment,each subscriber station that is a member of a multicast group isnotified about a start of a multicast call by an individual messageaddressed to the subscriber station. In one embodiment, the individualmessage comprises an individual multicast page (MCP). The concept of anindividual MCP is explained in the context of a communication system inaccordance with the IS-2000 standard. As conceptually illustrated inFIG. 3, a page message 300 may carry many pages 302, each destined for adifferent subscriber station or group of subscriber stations. The pagemessage 300 may comprise, e.g., a general page message (GPM) oruniversal page message (UPM) because either the GPM or the UPM can carrydifferent page record types. The page message is conveyed over the F-PCHor a forward common control channel (F-CCCH). The individual pages 302carried in a page message are referred to as page record types, eachpage record type comprising an address of the destined subscriberstation(s) 306, a type of the page 308 (i.e., individual or broadcast),a content 310 (i.e., the service option of the call), and otherinformation, e.g., sequence number 304. The addressing is specified in apage address type (ADDR_TYPE), e.g., a Temporary Mobile StationIdentifier (TMSI), an international mobile station identifier (IMSI),for individually addressing a subscriber station, or an address type foraddressing all subscriber stations. Upon receiving the page message 300,the subscriber station decodes address 306 to determine whether the page302 is intended for the subscriber station or not. If the address 306indicates that the page 302 is intended for the subscriber station, thesubscriber station decodes the type 308 to determine the type of call,and the content 310, to determine the details of the call. Each type ofa call, i.e., a voice call, a data call, an SO33 call in apoint-to-point communication system has a corresponding page record.Because, as discussed, the multicast call is a new type of a call, theindividual MCP must be defined as a new page record type.

[0064] The multicast call is advertised by including an identifier ofthe multicast group (GROUP_ID) into the individual MCP. The individualMCP is included in a page message and sent over a forward channel, e.g.,the FPCH or the F-CCCH, to the member subscriber stations, using themember subscriber stations' specific address. Additionally, the MCP mayprovide further information relevant to the advertised call, e.g., thetype of traffic channel assignments, type of bearer transport used, andother relevant information known to one of ordinary skills in the art.

[0065] An example of message flow in accordance with the abovedescribedembodiment is illustrated in FIG. 4. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. The sector S then determines the identity of thesubscriber stations MS_1 and MS_2, e.g., by querying a database.Alternatively, the sector S receives identity of the subscriber stationsMS_1 and MS_2. The sector S then creates an individual MCP containingthe identifier GROUP_IDx for subscriber stations MS_1 and MS_2.

[0066] One of ordinary skills in the art appreciates that a pagingchannel may operate in a slotted or non-slotted paging mode because suchmodes are described in documents known to ordinarily skilled artisans.As an example, such modes are described in the IS-95 standard, U.S. Pat.No. 5,392,287, entitled “METHOD AND APPARATUS FOR REDUCING POWERCONSUMPTION IN A MOBILE COMMUNICATION RECEIVER,” issued Feb. 21, 1995,assigned to the assignee of the present invention. For tutorial purposesFIG. 4 illustrates a configuration communication system, in which thesubscriber stations monitor the F-PCH or the F-CCCH in a slotted mode;however, one of ordinary skills in the art would understand that anon-slotted mode may be used. As one of ordinary skills in the artunderstands, the term slot refers to a partition of a physical channelwith a length expressed in time, number of chips or other appropriateunit.

[0067] The sector S waits until time t₂ for the paging slot assigned tothe subscriber station MS_1, and then conveys the individual MCP forMS_1 as part of a page message, e.g., the GPM, as shown. The subscriberstation MS_1 then may take an appropriate action, e.g., to initiatemonitoring the physical channel on which the multicast callcorresponding to the identifier GROUP_IDx is being transmitted, totransmit a response, to notify the user, and other actions in accordancewith design of a specific communication system. The sector S then waitsuntil time t₃ for the paging slot assigned to the subscriber stationMS_2, and then conveys the MCP for MS_2 as part of a page message, e.g.,the GPM, as shown. The subscriber station MS_2 then may take anappropriate action, as described above. In another embodiment, eachmember subscriber station is notified about a start of a multicast callby a common message addressed to the subscriber stations belonging tothe group. In one embodiment, the common message comprises a commonmulticast page (MCP). As explained above, because the common MCP isintended for a multiple, but not all, subscriber stations, and becausethe multicast call is a new type of a call, the common MCP must bedefined as a new page record type. Referring to the structure of a pagemessage 300 in FIG. 3 the new page record type 302 comprises a new pageaddress, multicast address (MC_ADDRESS) 304, specifying that the pagerecord type 302 is intended for a multiple subscriber stations, as wellas the type 308, the content 310, and other information, e.g., sequencenumber 304.

[0068] The start of a new multicast call is advertised by including anidentifier of the multicast group GROUP_ID, into the MCP for the membersubscriber stations, belonging to the multicast group identified by theGROUP_ID. The common MCP is included in a page message and sent over aforward channel, e.g., the F-PCH or the F-CCCH, to the subscriberstations for which the common MCP is intended, using the MC_ADDRESS.Additionally, the MCP may provide further information relevant to theadvertised call, e.g., the type of traffic channel assignments, type ofbearer transport used, and other relevant information known to one ofordinary skills in the art. However, as explained above, in currentcommunication systems, a subscriber station is assigned to monitor apaging channel slot in which a page for the subscriber station is to besent. However, the subscriber stations belonging to the group identifiedby the GROUP_ID are not necessarily assigned the same slot on the pagingchannel. Furthermore, the entity, responsible for paging, e.g., a basestation controller (BSC) may not know which subscriber stations aremembers of a particular multicast group, consequently, the BSC cannotperform the mapping between an individual subscriber station and theMC_ADDRESS. Such a scenario occurs e.g., when multicast service isprovided over Internet protocol (IP) because the MCP is triggered due toreceiving an IP packet over a multicast IP address. Therefore, a methodenabling efficient method for delivering the multicast call initiationinformation is required. Consequently, in accordance with oneembodiment, the common MCP is sent in the first slot of a broadcastpaging cycle (BPC). The concept of BPC is explained in terms of a pagingchannel as implemented in a communication system in accordance with theIS-2000 standard. As illustrated in FIG. 5, the F-PCH and the F-CCCH aredivided into slots. To enable periodic broadcast paging, a broadcastpaging cycle is defined in terms of duration (in number of F-PCH/F-CCCHslots) given as follows:

BPC=B+X  (1)

[0069] where B is given as follows:

B=2^(i)×16, where 1≦i≦7 for F-PCH and 2≦i≦8 for F-CCCH   (2)

[0070] and X is a fixed offset. For example in a communication system inaccordance with the IS-2000 standard, the values are 3 on the F-PCH and7 on F-CCCH.

[0071] The value of a broadcast index i (BCAST_INDEX) is transmitted bythe sector in the Extended System Parameters Message (ESPM) for F-PCHand Multicarrier Radio Resource Parameters Message (MCRR) for F-CCCH.

[0072] A subscriber station in a slotted mode monitors a slot, isdetermined in accordance with the following equation:

B=2^(i)×16, where 1≦j≦7 for F-PCH and 2≦j≦8 for F-CCCH   (3)

[0073] where the value of a slot index j (BCAST_INDEX) is transmitted bythe sector in the Extended System Parameters Message (ESPM) for F-PCHand Multicarrier Radio Resource Parameters Message (MCRR) for F-CCCH.

[0074] As a consequence, for any combination of the broadcast index iand a slot index j, there would be a collision between a broadcast slot,which the subscriber station monitors for broadcast in accordance withthe Equation (2), and a slot monitored by the subscriber station forindividually addressed messages in slotted mode in accordance with theEquation (3). The collision would be repeated in the same slot;consequently, the subscriber station monitoring the particular slotwould always encounter a collision between the multicast page and theindividual page. Introduction of the offset X into Equation (2)resulting in Equation (1) does not completely eliminate the collision,but prevents the collision to occur in periodically in the same slot,therefore, the collision is spread among all the subscriber stations.Thus, each subscriber station can decode either message in anon-affected slot.

[0075] The first slot of each BPC is an F-PCH/F-CCCH slot, for which thefollowing Equation holds:

t/4mod(BPC)=t/4mod(B+X)=0  (3)

[0076] where t represents system time expressed in frames; and

[0077] mod means a modulo arithmetic.

[0078] Such an arrangement would require each subscriber station to wakeup and monitor not only a slot individually assigned to the mobile forother types of messages, but also every first slot of the BPC of theF-PCH/F-CCCH, thus, increasing power consumption. To avoid such powerconsumption, slots of a forward quick paging channel (F-QPCH),associated with a F-PCH/F-CCCH, contain Broadcast Indicator (BI) bitsthat are used to inform subscriber stations monitoring the F-QPCH aboutoccurrence or non-occurrence of the common MPC on the first slot of theBPC of the corresponding F-PCH/F-CCCH. If there is a common MPC on thefirst slot of the BPC of the F-PCH/F-CCCH, the BI bits of thecorresponding F-QPCH slot are turned ON, resulting in subscriberstations starting to monitor the first slot of the BPC on theF-PCH/F-CCCH. Although a subscriber station is required to wake up andmonitor the BI bits of the first F-QPCH slot of the BPC, because theduration of the BI is much shorter than the duration of the slot of aF-PCH/F-CCCH, the wake up interval is shorter, therefore, batteryconsumption is achieved.

[0079] A disadvantage of the above-described embodiment is that becausethe MCP for all multicast calls are sent on the first slot of the BPC onthe F-PCH/F-CCCH, the BI bits on the corresponding F-QPCH are set to ON,when the MCP is present. Consequently, each subscriber stationmonitoring the BI indicator must wake up and monitor the first slot onthe F-PCH/F-CCCH to determine, whether the MCP is intended to thesubscriber station. Therefore, the subscriber stations not belonging tothe multicast group for which the MCP is intended still increase powerconsumption. As illustrated in FIG. 5, a GPM, containing a common MCPfor subscriber stations MS₁ and MS₂ belonging to a multicast group(GC_1), is transmitted in the first slot of a BPC on the F-PCH/F-CCCH(Slot O_p). However, because the BI bits in the corresponding slot ofthe F-QPCH (Slot 0_q) is set ON, all subscriber stations MS₁-MS₄, mustwake up and monitor the Slot 0_p of the F-PCH/F-CCCH. Similarly, a GPM,containing a common MCP for subscriber stations MS₃ belonging to amulticast group (GC_2) is transmitted in the first slot of the next BPCof the F-PCH/F-CCCH (Slot 4_p). Therefore, the BI bits in thecorresponding slot of the F-OPCH (Slot 4_q) is set ON and all subscriberstations MS₁- MS₄, must wake up and monitor the Slot 4_p of theF-PCH/FCCCH, although the GPM contains only a common MCP intended for asubscriber station MS₃.

[0080] One of ordinary skills in the art recognizes that theabove-described embodiment utilized the first slot of the BPC as aconcession to an existing standard. Consequently, such a limitation isunnecessary in general, and any slot of the BPC pre-agreed upon by theaccess network and the subscriber stations can be used. Consequently, inaccordance with another embodiment, the limitation that the MPC may besent in only the first slot of a BPC on the F-PCH/F-CCCH is removed. Forterminology consistency reasons, the term BPC is replaced by a termmulticast paging cycle (MPCY). One of ordinary skills in the artunderstands that the concepts of BPC and MPCY are identical. Because itis still desired that a subscriber station does not wake up to monitorevery slot of the F-PCH/F-CCCH, it is necessary to establish aprocedure, allowing the sector to determine, in which slot to send amessage to a particular multicast group, and allowing subscriberstation(s) belonging to the multicast group to determine, which slot tomonitor. The procedure is defined by a mapping function, e.g., a hashfunction, accepting input parameters, e.g., the total number of slots inthe MPCY, and a GROUP_ID, and outputting a number, which identifies theslot, in which a paging message, containing common MPC for subscriberstations belonging to the multicast group identified by that GROUP_ID,will be transmitted. Alternatively, the mapping can be implemented as atable or any other algorithm mapping the GROUP_ID to a slot number.Because a subscriber station is given a GROUP_ID of each group, to whichthe subscriber station belong, e.g., upon subscription to the group; thesubscriber station may use the hash function to determine the F-QPCHslot to monitor to read the BI indicator. This reduces the probabilityof false alarm, i.e., the subscriber station waking up for a MCP for aMulticast Group to which the subscriber station does not belong. One ofordinary skills in the art understands that a hash function has beenused only as an example, and any other mapping function, allowing boththe access network and the subscriber station arrive at the same slotgiven the same input parameters, is acceptable.

[0081] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 6. At an instant t₁ a sector Sreceives an indication GROUP_IDx from a source of information (notshown) that a multicast call intended for group with GROUP_IDx,comprising subscriber stations MS_1 and MS_2 is to start. As discussed,such a source of information may comprise e.g., a server, anothersubscriber station, or another source. The sector S creates the commonMCP containing the GROUP_IDx for subscriber stations MS_1 and MS_2, andenters the GROUP_IDx together with the number of slots of the MPCY intoa mapping function. Referring to FIG. 7, the hash function returns anindication that the MCP for the GROUP_IDx is to be sent in Slot 0_p. Atan instant t₂, indicating beginning of slot (Slot 0_q) of F-QPCHcorresponding to Slot 0_p of F-CCCH, the sector S sets BI bit to ON. Thesubscriber stations MS_1 and MS_2, that used the same hashing functionto determine which slot of F-QPCH to monitor, detect that the BI bit inthe Slot 0_q is set to ON. The subscriber stations MS_1 and MS_2 thenwake up for monitoring of Slot 0_p at instant t₃. At the instant t₃,indicating beginning of Slot 0_p the sector S transmits the MCP as apart of the page message, e.g., the GPM.

[0082] As indicated in FIG. 5, MS_3 is a member of a multicast groupdifferent from the multicast group indicated by GROUP_IDx. Because norequest for multicast call for the multicast group to which MS_3 belonghas been received, no notification is needed in Slot 1_p of the F_CCCH,and the BI bits in a slot of F-QPCH corresponding to Slot 1_q of F_CCCH,are set to OFF.

[0083] In another embodiment, the subscriber stations are informed abouta multicast call over protocol layers higher than an air interfacesignaling layer. As is known in the art, layering is a method fororganizing communication protocols in well-defined encapsulated dataunits between otherwise de-coupled processing entities, i.e., layers.The protocol layers are implemented in both base stations 110 and remotestations 116. In accordance with the Open Systems Interconnection (OSI)model, protocol layer L1 provides for the transmission and reception ofradio signals between the base station and remote station, layer L₂provides for the correct transmission and reception of signalingmessages, and layer L3 provides for the control messaging for thecommunication system. Layer L3 originates and terminates signalingmessages according to the semantics and timing of the communicationprotocol between a base station 110 and a remote station 116. In acdma2000 system, the air interface signaling layer L1 is referred to asthe Physical Layer, L2 is referred to as the Link Access Control (LAC)Layer or the Medium Access Control (MAC) Layer, and L3 is referred to asthe Signaling Layer. Above the Signaling Layer are layers, which inaccordance with the OSI model are numbered L4-L7 and referred to asTransportation, Session, Presentation and Application Layers.

[0084] In accordance with the embodiment, a link layer session isestablished between the source of information and a subscriber stationusing an existing communication system interface. Such a link layerprotocol can comprise, e.g., a point-to-point protocol (PPP), a SerialLine Internet Protocol (SLIP), or other link layer protocol known to oneof ordinary skills in the art may be utilized without departing from thescope of the present invention. Link layer protocols are described indocuments known to ordinarily skilled artisans, e.g., IS-707 standard.The multicast call notification message is then sent via Internetprotocol (IP) connection of the link layer session.

[0085]FIG. 8 illustrates an example of message flow in accordance withone embodiment. At an instant t₁, a sector S receives an indicationPage(MS_1 from a source of information via a Packet Service Data Node(PSDN) that a multicast call intended for group comprising subscriberstation MS_1 is to start. The sector S generates a page record intendedfor the subscriber station MS_1 for a call set-up requesting a PPP (DP).Because the requested call is a point-to-point type of a call, the pagerecord is an individual for each member subscriber station. Inaccordance with an IS-707, such a service option is SO33. As discussedabove, the service option is included in the content part of a pagerecord. The sector S then generates an appropriate page message, e.g., aGPM, and waits until time t₂ for the paging slot assigned to thesubscriber station MS_1. At time t₂, the page message is transmitted asa part of a GPM(DP:SO33) to MS_1. In one embodiment, the subscriberstation MS_1 acknowledges receipt of the MCP at time t₃. As illustratedin FIG. 8, in a communication system in accordance with the IS-2000standard, the response comprises page response message (PRM(SO33)),which is modulated on a reverse channel, e.g. an access channel. At timet₄, the sector S sends a notification which channel is the multicastcall to use. In a communication system in accordance with the IS-2000standard such a notification is sent in an extended channel assignmentmessage (ECAM). Consequently, an SO33 call is established on the channelassigned by the ECAM. Once the SO33 call is established, the PPP betweenthe source PDSN and the subscriber station MS_1 is established at timet₅. The MS_1 is then notified about the multicast call commencement overthe PPP. The remaining subscriber stations belonging to the multicastgroup and interested in the multicast call follow the above describedprocedure. (Only one additional subscriber station MS_2 is shown forsimplicity.) In accordance with another embodiment, upon receiving anotification about a multicast call to a group identified by a GROUP_IDfrom a source, the sector transmits a multicast addressed page record toall subscriber station in the group, for which the multicast call isintended, requesting establishment of a link layer protocol. Asdiscussed above, the subscriber stations belonging to the groupidentified by the GROUP_ID are not necessarily assigned the same slot onthe paging channel. Consequently, any of the solutions described aboveto properly deliver the multicast addressed page are applicable.

[0086] Once a subscriber station belonging to the group responds to themulticast addressed page by sending a PRM, the sector sets up the linklayer protocol, e.g., a SO33 call with the subscriber station asdescribed above, and notifies the subscriber station are about themulticast call commencement over the link layer protocol. The link layerprotocol call set up and the notification is then repeated for eachremaining subscriber station. Such an individual link layer protocol setup is possible because although the access network did not necessarilyknow the identities of the individual subscriber station upon sendingthe multicast addressed page, upon receiving the responses fromsubscriber stations the identities were revealed.

[0087] Response to Notification of Multicast Call Commencement

[0088] As discussed above, when a multicast call is to be initiated, thesubscriber stations that are members of the multicast group must benotified. Once a subscriber station receives a notification that amulticast call is commencing, there are several alternatives for whetherand how the subscriber station responds to the notification.

[0089] According to one alternative, the subscriber station is notrequired to respond even if the subscriber station is interested inparticipation in the multicast service. Such an alternative isacceptable for example in the case of multicast services, which are ofgeneral interest and delivery of which to each subscriber station is notcritical, e.g., stock market information updates, streaming video, andother information of similar nature.

[0090] According to another alternative, the subscriber station isalways required to respond if the subscriber station is interested inparticipation in the multicast service. The response comprises e.g., amessage send on a reverse channel to the access network. An example ofsuch a message in a communication system in accordance with the IS-2000standard is a Page Response Message transmitted on a reverse accesschannel (R-ACH), reverse enhanced access channel (R-EACH), and reversecommon control channel (R-CCCH). Such a response must containinformation useful for the next action taken by the access network.Depending on design features of a communication system, such informationmay indicate whether the subscriber station is interested in joining themulticast service; whether the subscriber station is not interested injoining the multicast service; whether the subscriber station isinterested but cannot participate due to not supporting the requiredconfiguration, e.g., a data rate.

[0091] The access network waits for response from member subscriberstations before channel assignment. Such an alternative is required forservices, requiring the access network to know whether each subscriberstation participates. Additionally, the response allows the accessnetwork to decide, whether to assign a shared channel or a dedicatedchannel for the multicast content. When a decision to assign a dedicatedchannel to each subscriber station is made, the response prevents theaccess network from assigning a dedicated traffic channel to anon-participating subscriber station.

[0092] As explained above, in one embodiment, each subscriber stationthat is a member of a multicast group is notified about a start of amulticast call intended for the group by a common message addressed tothe member subscriber stations. When a subscriber station that is not amember of the group identified in the common message receives anotification, the subscriber station may ignore the notification and notrespond. However, if an AdHoc multicast group formation is supported,all the subscriber station receiving the notification may be required torespond. The term AdHoc multicast group is used herein to mean amulticast group that is not pre-determined, but is created uponinitiation of the multicast call. Whether an AdHoc multicast groupformation is supported or not, the requirement of response to the commonmessage notification elicits responses from the subscriber stations thatreceived the notification. Because numerous subscriber stations mayrespond, a method for staggering the response message, e.g., a PageResponse Message from the subscriber stations in the group, may beimplemented to avoid a collision from a burst of responses.

[0093] According to another alternative, the subscriber station isalways required to respond, even if the subscriber station is notinterested in participation in the multicast service. Such analternative is required for services, requiring the access network toknow with certainty whether each subscriber station participates. Unlikethe previous alternative, the present alternative allows the accessnetwork to differentiate with certainty between subscriber stations thatdo not respond due to no interest in the multicast service, andsubscriber stations that do not respond due to failure to receive anotification. Thus, the access network may take appropriate action,e.g., repeat the notification. The remaining consideration as describedwith regards to the previous alternative are applicable.

[0094] It will be understood by one of ordinary skills in the art thatthe above-described alternatives were treated separately for tutorialpurposes only. A communication system will use any alternativeappropriate for a multicast service. For example, when a multicast call,delivery of which to each subscriber station is not critical, is tocommence, no response may be required from the member subscriberstations. When the same member subscriber stations need to participatein a subsequent multicast call, a response may be required. Theindication whether and what response is required by the access networkcan be indicated to the subscriber stations, e.g., by a signalingcontained in the notification message. However, any other means ofresponse indication is contemplated.

[0095] Channel Assignment for a Multicast Call Commencement

[0096] As alluded to above, the communication system 100 provides thecontent over a forward link channel 114 to the member subscriberstations. Consequently, the forward link channel, whether shared amongthe member subscriber stations or established individually between eachmember subscriber station and a base station, must be assigned by anentity of the communication system 100 before the multicast service maycommence.

[0097] As described above, there are several methods of notification,several methods of response, and several methods of channel assignments.Consequently, several possible combinations of notification, response,and channel assignments are possible as described in the embodimentsbelow.

[0098] As discussed, in one embodiment, the member subscriber stationsare notified about the multicast service via a common overhead messageor a common page message. Because the multicast service notification isbroadcasted in a common message to multiple subscriber station, and notto an individual subscriber station, the entity generating the commonmessage does not need to know the identities of individual membersubscriber stations of the multicast group.

[0099] If the member subscriber stations are not required to respond,the channel assignment information for the multicast service trafficchannel, e.g., channel identification (Walsh Code in case of acommunication system in accordance with IS-2000 standard), data rate,and other assignment information known to one of ordinary skills in theart may be included as part of the notification. Consequently, in caseof notification via a common overhead message, the channel assignmentinformation would be part of the overhead message; in case ofnotification via a common page message, the channel assignmentinformation is part of the MCP. Because the channel assignmentinformation is multicasted and no response is required, the type ofchannel assigned must be a shared channel. Alternatively, the channelassignment information may be conveyed to the subscriber stationsseparate from the notification.

[0100] Once the subscriber station processes the message, the interestedsubscriber station(s) start to monitor the assigned channel to receivemulticast service traffic.

[0101] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 9. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2, e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art.

[0102] The sector S includes the identifier and the channel assignmentinformation into the overhead message, which in one embodiment comprisesa broadcast system parameters message BSPM. The sector S broadcasts theBSPM(GROUP_IDx, Channel Assignment Information) at time t_(2o).Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx, Channel Assignment Information),process the BSPM and take an appropriate action at time t₃, e.g., tuneto and start monitoring the physical channel on which the identifiedmulticast call is being transmitted. At time t₄ the content of themulticast service starts to be transmitted on the traffic channel(Traffic for Group_IDx). As discussed, the overhead message BSPM repeatsitself periodically, consequently, if the identifier and the channelassignment information is included in each message, likewise, theidentifier and the channel assignment information will be transmitted inthe next instance(s) of the overhead message BSPM. Only one instance attime t_(2o) is shown.

[0103] Alternatively, the sector S includes the identifier and thechannel assignment information into a page message, e.g. a general pagemessage (GPM). The sector S determines the slot on a paging channelmonitored by the member subscriber stations using any of theabove-described embodiments. The section then transmits theGPM(MCP:GROUP_IDx, Channel Assignment Information) in the slot at timet_(2p). Subscriber stations MS_1 and MS_2 that are members of the groupwith the identifier receive the GPM(MCP:GROUP_IDx, Channel AssignmentInformation), process the GPM and take an appropriate action at time t₃,e.g., tune to and start monitoring the physical channel on which theidentified multicast call is being transmitted. At time t₄ the contentof the multicast service starts to be transmitted on the traffic channel(Traffic for Group_IDx).

[0104] If the member subscriber stations are required to respond priorto channel assignment, upon receiving the multicast service notificationin the common message, the interested subscriber stations send aresponse. Such a response may comprise e.g., a signaling message (a newtype of message, e.g., a Multicast Service Join Message as a response tothe common overhead message or a Page Response Message as a response tothe common page message), indicating the interested subscriber stations'desire to participate in the multicast service.

[0105] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment may take the number of responsesinto account in determining the type of channel to assign. In oneembodiment, the access network compares the number of responses to athreshold, and assigns the type of channel in accordance with the resultof the comparison. If the entity decides to assign a shared channel, theaccess network sends a common channel assignment message, e.g., aMulticast Channel Assignment Message (MCAM), containing information forthe shared multicast service traffic channel. Thus, the MCAM uses amulticast address to assign the shared channel to the interestedsubscriber stations.

[0106] As has been explained above, the subscriber stations belonging tothe group identified by the GROUP_ID are not necessarily assigned thesame slot on the paging channel. Consequently, a method enablingefficient method for delivering the multicast call initiationinformation is required.

[0107] In one embodiment, upon receiving the notification, thesubscriber stations are required to monitor the paging channel in anon-slotted mode; consequently, the MCAM may be sent in any pagingchannel slot.

[0108] In another embodiment, the MCAM is sent on a slot using the samemethod employed for determining a slot to send a multicast-addressednotification.

[0109] In another embodiment, the common overhead message or the commonpage message indicates the paging channel slot number, which thesubscriber stations are required to monitor for the MCAM.

[0110] In another embodiment, the MCAM is sent on each of the slotsmonitored by the subscriber stations.

[0111] It will be understood by one of ordinary skills in the art, thatthe embodiments described were treated separately for tutorial purposesonly. A communication system will use an embodiment appropriate for amulticast service. The selection of the embodiment may be specifiede.g., in the notification.

[0112] Once the subscriber station processes the message, the subscriberstation(s) interested start to monitor the assigned channel to receivemulticast service traffic.

[0113] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 10. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2, e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art.

[0114] The sector S includes the identifier into the overhead message,which in one embodiment comprises a broadcast system parameters messageBSPM. The sector S broadcasts the BSPM(GROUP_IDx) at time t_(2o).Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx), process the BSPM and take anappropriate action, e.g., send a response message. As discussed, theoverhead message BSPM repeats itself periodically, consequently, if theidentifier is included in each message, the identifier will betransmitted in the next instance(s) of the overhead message BSPM. Onlyone instance at time t_(2o) is shown.

[0115] Alternatively, the sector S includes the identifier into a pagemessage, e.g. a general page message (GPM). The sector S then determinesthe slot on a paging channel monitored by the member subscriberstations, and transmits the GPM(MCP:GROUP_IDx) in the slot at timet_(2p). Subscriber stations MS_1 and MS_2 that are members of the groupwith the identifier receive the GPM(MCP:GROUP_IDx), process the GPM andtake an appropriate action, e.g., send a response message.

[0116] Regardless of what common message was used for notification, thesubscriber stations MS_1 and MS_2 send response at time t₃, respectivet₄. Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign a sharedchannel. The sector S determines the method of sending the commonchannel assignment message, e.g., the MCAM, and sends the MCAMcontaining information for the shared multicast service traffic channelMCAM(Channel Assignment Information) at time t₅. The subscriber stationsMS_1 and MS_2 process the MCAM and take an appropriate action, e.g.,tune to and start monitoring the physical channel on which theidentified multicast call is being transmitted at time t₆. At time t₇the content of the multicast service starts to be transmitted on thetraffic channel (Traffic for Group_IDx).

[0117] In another embodiment, if the entity decides to assign a sharedchannel, the access network sends an Individual Channel AssignmentMessage (ICAM), containing information for the shared multicast servicetraffic channel to each responding member subscriber station. In thecontext of a communication system in accordance with the IS-2000standard, the ICAM can comprise, e.g., an Extended Channel AssignmentMessage.

[0118] Such an individual assignment is possible because, although theaccess network did not necessarily know the identities of the individualsubscriber station when sending the notification, upon receiving theresponses from subscriber stations the identities were revealed.

[0119] It is noted that because the shared multicast service trafficchannel is assigned individually as in a point-to-point call, any methodknown for a point-to-point traffic channel assignment can be used.Consequently, the issue of when to send the ICAM for each subscriberstation is not present because the access network knows when each of theinterested subscriber stations will be monitoring the paging channel.

[0120] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 11. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2, e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art.

[0121] The sector S includes the identifier into the overhead message,which in one embodiment comprises a broadcast system parameters messageBSPM. The sector S broadcasts the BSPM(GROUP_IDx) at time t_(2o).Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx), process the BSPM and take anappropriate action, e.g., send a response message. As discussed, theoverhead message BSPM repeats itself periodically, consequently, if theidentifier is included in each message, the identifier will betransmitted in the next instance(s) of the overhead message BSPM. Onlyone instance at time t_(2o) is shown.

[0122] Alternatively, the sector S includes the identifier into a pagemessage, e.g. a general page message (GPM). The sector S then determinesthe slot on a paging channel monitored by the member subscriberstations, and transmits the GPM(MCP:GROUP_IDx) in the slot at timet_(2p). Subscriber stations MS_1 and MS_2 that are members of the groupwith the identifier receive the GPM(MCP:GROUP_IDx), process the GPM andtake an appropriate action, e.g., send a response message.

[0123] Regardless of what common message was used for notification, thesubscriber stations MS_1 and MS_2 send response at time t₃, respectivet₄. Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign dedicatedchannels. Because the sector S knows the identity of the subscriberstations MS_1 and MS_2 from the responses received, the sector Sdetermines the slot in which the subscriber stations MS_1 and MS_2 willbe monitoring the paging channel in accordance with the response. Thesector S waits until time t₅ for the paging slot monitored by thesubscriber station MS_1, and then conveys the individual ICAM(ChannelAssignment Information) to the subscriber station MS_1. Similarly, thesector S waits until time t₆ for the paging slot monitored by thesubscriber station MS_2, and then conveys the individual ICAM(ChannelAssignment Information) subscriber station MS_2. The subscriber stationsMS_1 and MS_2 process the ICAM and take an appropriate action, e.g.,tune to and start monitoring the physical channel on which theidentified multicast call is being transmitted at time t₅ respective t₆.At time t₇ the content of the multicast service starts to be transmittedon the traffic channel (Traffic for Group_IDx).

[0124] In another embodiment, if the entity decides to assign adedicated channel for each responding member subscriber station, theaccess network sends an individual channel assignment message,containing information for the dedicated multicast service trafficchannels to each responding member subscriber station.

[0125] Such an individual assignment is possible because although theaccess network did not necessarily know the identities of the individualsubscriber station when sending the notification, upon receiving theresponses from subscriber stations the identities were revealed.

[0126] Because the multicast service traffic channel is assignedindividually as in a point-to-point call, any method known for apoint-to-point traffic channel assignment can be used. Specifically, theaccess network knows when each of the interested subscriber stationswill be monitoring the paging channel.

[0127] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 12. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2, e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art.

[0128] The sector S includes the identifier into the overhead message,which in one embodiment comprises a broadcast system parameters messageBSPM. The sector S broadcasts the BSPM(GROUP_IDx) at time t_(2o).Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx), process the BSPM and take anappropriate action, e.g., send a response message. As discussed, theoverhead message BSPM repeats itself periodically, consequently, if theidentifier is included in each message, the identifier will betransmitted in the next instance(s) of the overhead message BSPM. Onlyone instance at time t_(2o) is shown.

[0129] Alternatively, the sector S includes the identifier into a pagemessage, e.g. a general page message (GPM). The sector S then determinesthe slot on a paging channel monitored by the member subscriberstations, and transmits the GPM(MCP:GROUP_IDx) in the slot at timet_(2p). Subscriber stations MS_1 and MS_2 that are members of the groupwith the identifier receive the GPM(MCP:GROUP_IDx), process the GPM andtake an appropriate action, e.g., send a response message.

[0130] Regardless of what common message was used for notification, thesubscriber stations MS_1 and MS_2 send response at time t₃, respectivet₄. Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign dedicatedchannels. Because the sector S knows the identity of the subscriberstations MS_1 and MS_2 from the responses received, the sector Sdetermines the slot in which the subscriber stations MS_1 and MS_2 willbe monitoring the paging channel in accordance with the response.

[0131] The sector S waits until time t₅ for the paging slot monitored bythe subscriber station MS_1, and then conveys the individualICAM(Channel Assignment Information) to the subscriber station MS_1. Thesubscriber station MS_1 processes the ICAM and take an appropriateaction, e.g., tunes to and starts monitoring the physical channel onwhich the identified multicast call is being transmitted at time t₅.

[0132] Similarly, the sector S waits until time t₇ for the paging slotmonitored by the subscriber station MS_2, and then conveys theindividual ICAM(Channel Assignment Information) subscriber station MS_2.The subscriber station MS_2 processes the ICAM and takes an appropriateaction, e.g., tunes to and starts monitoring the physical channel onwhich the identified multicast call is being transmitted at time t₆.

[0133] At time t₇ the content of the multicast service starts to betransmitted on the dedicated traffic channels (Traffic for Group_IDx).

[0134] In another embodiment, if the entity decides to assign adedicated channel for each responding member subscriber station, theaccess network sends a common channel assignment message, MulticastChannel Assignment Message (MCAM), containing information for each ofthe individual multicast service traffic channel. Thus, one MCAMutilizing a multicast address assigns for each interested subscriberstations a dedicated multicast service traffic channel.

[0135] As has been explained above, the subscriber stations belonging tothe group identified by the GROUP_ID are not necessarily assigned thesame slot on the paging channel. Consequently, a method enablingefficient method for delivering the multicast call initiationinformation is required.

[0136] In one embodiment, upon receiving the notification, thesubscriber stations are required to monitor the paging channel in anon-slotted mode; consequently, the MCAM may be sent in any pagingchannel slot.

[0137] In another embodiment, the MCAM is sent on a slot using the samemethod employed for determining a slot to send a multicast-addressednotification.

[0138] In another embodiment, the common overhead message or the commonpage message indicates the paging channel slot number, which thesubscriber stations are required to monitor for the MCAM.

[0139] In another embodiment, the MCAM is sent on each of the slotsmonitored by the subscriber stations.

[0140] It will be understood by one of ordinary skills in the art, thatthe embodiments described were treated separately for tutorial purposesonly. A communication system will use an embodiment appropriate for amulticast service. The selection of the embodiment may be specifiede.g., in the notification.

[0141] Once the subscriber station processes the message, the subscriberstation(s) interested start to monitor the assigned channel to receivemulticast service traffic.

[0142] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 11. At an instant t₁, a sector Sreceives an indication GROUP_IDx that a multicast call intended forgroup with an identifier GROUP_IDx is to start. The indication may beprovided by another entity of the communication system, e.g., a basestation controller, a PSTN, a source of information (not shown), another entities. Alternatively, the sector S receives identity of thesubscriber stations MS_1 and MS_2. The sector S then determines theidentifier of the multicast group GROUP_IDx comprising the subscriberstations MS_1 and MS_2 e.g., by querying a database. As discussed, thesource of information may comprise, e.g., a server, another subscriberstation, or any other source known to one skilled in the art.

[0143] The sector S includes the identifier into the overhead message,which in one embodiment comprises a broadcast system parameters messageBSPM. The sector S broadcasts the BSPM(GROUP_IDx) at time t_(2o).Subscriber stations MS_1 and MS_2 that are members of the group with theidentifier receive the BSPM(GROUP_IDx), process the BSPM and take anappropriate action, e.g., send a response message. As discussed, theoverhead message BSPM repeats itself periodically, consequently, if theidentifier is included in each message, the identifier will betransmitted in the next instance(s) of the overhead message BSPM. Onlyone instance at time t_(2o) is shown.

[0144] Alternatively, the sector S includes the identifier into a pagemessage, e.g. a general page message (GPM). The sector S then determinesthe slot on a paging channel monitored by the member subscriberstations, and transmits the GPM(MCP:GROUP_IDx) in the slot at timet_(2p). Subscriber stations MS_1 and MS_2 that are members of the groupwith the identifier receive the GPM(MCP:GROUP_IDx), process the GPM andtake an appropriate action, e.g., send a response message.

[0145] Regardless of what common message was used for notification, thesubscriber stations MS_1 and MS_2 send response at time t₃, respectivet₄. Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign a dedicatedchannel. The sector S determines the method of sending the commonchannel assignment message, e.g., the MCAM, and sends the MCAMcontaining information for the dedicated multicast service trafficchannel MCAM(Channel Assignment Information) at time t₅.

[0146] The subscriber station MS_1 processes the MCAM and take anappropriate action, e.g., tunes to and starts monitoring the physicalchannel on which the identified multicast call is being transmitted attime t₆.

[0147] Similarly, the subscriber station MS_2 processes the ICAM andtakes an appropriate action, e.g., tunes to and starts monitoring thephysical channel on which the identified multicast call is beingtransmitted at time t₆.

[0148] At time t₇ the content of the multicast service starts to betransmitted on the dedicated traffic channels (Traffic for Group_IDx).

[0149] In one embodiment, each member subscriber station is notifiedabout the multicast service via an individual page message. Because themulticast service notification is transmitted via a multiple ofindividual page messages to multiple subscriber stations, the entitygenerating the individual page messages needs to know the identities ofindividual member subscriber stations.

[0150] If the member subscriber stations are not required to respond,the channel assignment information for the multicast service trafficchannel, e.g., channel identification (Walsh Code in case of acommunication system in accordance with IS-2000 standard), data rate,and other assignment information known to one of ordinary skills in theart may be included as part of the notification. Consequently, in caseof notification via the individual page message, the channel assignmentinformation would be part of the individual page message. Because thechannel assignment information is provided in the individual pagemessage, the type of channel assigned may be both a shared channel and adedicated channel.

[0151] Because the member subscriber stations are not required torespond to the multicast service notification, in case that the entitygenerating the individual page messages decides to assign a dedicatedchannel to each member subscriber station, the entity may be allocatingdedicated resources for member subscriber station that may not beinterested in participating in the multicast service. Therefore, it isdesirable to determine, whether a member subscriber station that wasassigned a dedicated channel is or is not interested in participating inthe multicast service, so that the dedicated channel for thenon-participating member subscriber station may be reclaimed, and reusedfor other service, e.g., a regular point-to-point call. In oneembodiment, the access network, after the dedicated channels has beenassigned and the multicast service has commenced, determines whether themember subscriber stations are active on the assigned reverse linkchannel.

[0152] Once the subscriber station processes the message, the subscriberstation(s) interested start to monitor the assigned channel to receivemulticast service traffic.

[0153] An example of message flow in accordance with the above-describedembodiment, in which a shared channel is assigned, is illustrated inFIG. 14. At an instant t₁, a sector S receives an identity of thesubscriber stations MS_1 and MS_2 GROUP_IDx, comprising a group with anidentifier GROUP_IDx, for which a multicast call is to start.Alternatively, the sector S receives a group identifier GROUP_IDx. Theinformation may be provided by another entity of the communicationsystem, e.g., a base station controller, a PSTN, a source of information(not shown), an other entities. The sector S then determines theidentity of the subscriber stations MS_1 and MS_2, e.g., by querying adatabase. The sector S then creates an individual MCP containing theidentifier GROUP_IDx and a channel assignment information for eachsubscriber station MS_1 and MS_2, and includes the MCP into a pagemessage, e.g. a general page message (GPM).

[0154] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx, Channel Assignment Info). Subscriberstation MS_1 receives the GPM(MCP:GROUP_IDx, Channel Assignment Info),processes the GPM and takes an appropriate action, e.g., tunes to andstarts monitoring the physical channel on which the identified multicastcall is being transmitted.

[0155] At time t₂, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx, Channel AssignmentInfo). Subscriber station MS_2 receives the GPM(MCP:GROUP_IDx, ChannelAssignment Info), processes the GPM and take an appropriate action,e.g., tunes to and starts monitoring the physical channel on which theidentified multicast call is being transmitted.

[0156] At time t₄ the content of the multicast service starts to betransmitted on the shared traffic channel (Traffic for Group_IDx).

[0157] An example of message flow in accordance with the above-describedembodiment, in which dedicated channels are assigned, is illustrated inFIG. 15. At an instant t₁, a sector S receives an identity of thesubscriber stations MS_1 and MS_2 GROUP ID_x comprising a group with anidentifier GROUP_IDx, for which a multicast call is to start.Alternatively, the sector S receives a group identifier GROUP_IDx. Theinformation may be provided by another entity of the communicationsystem, e.g., a base station controller, a PSTN, a source of information(not shown), an other entities. The sector S then determines theidentity of the subscriber stations MS_1 and MS_2, e.g., by querying adatabase. The sector S then creates an individual MCP containing theidentifier GROUP_IDx and a channel assignment information for eachsubscriber station MS_1 and MS_2, and includes the MCP into a pagemessage, e.g. a general page message (GPM).

[0158] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx, Channel Assignment Info for MS_1).Subscriber station MS_1 receives the GPM(GROUP_IDx, Channel AssignmentInfo for MS_1), processes the GPM and takes an appropriate action, e.g.,tunes to and starts monitoring the physical channel on which theidentified multicast call for the subscriber station MS_1 is beingtransmitted (Traffic for MS_1) at time t₃.

[0159] At time t₄, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx, Channel AssignmentInfo for MS_2). Subscriber station MS_2 receives the GPM(GROUP_IDx,Channel Assignment Info for MS_2), processes the GPM and take anappropriate action, e.g., tunes to and starts monitoring the physicalchannel on which the identified multicast call for the subscriberstation MS_2 is being transmitted (Traffic for MS_2) at time t₃.

[0160] If the member subscriber stations are required to respond priorto channel assignment, upon receiving the multicast service notificationin the individual page messages, the interested subscriber stations senta response, e.g., a signaling message like a Page Response Message,indicating the interested subscriber stations' desire to participate inthe multicast service.

[0161] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment may take the number of responsesinto account in determining the type of channel to assign. In oneembodiment, the access network compares the number of responses to athreshold, and assigns the type of channel in accordance with the resultof the comparison. If the entity decides to assign a shared channel, theaccess network sends a common channel assignment message, e.g., aMulticast Channel Assignment Message (MCAM), containing information forthe shared multicast service traffic channel. Thus, the MCAM uses amulticast address to assign the shared channel to the interestedsubscriber stations.

[0162] As has been explained above, the subscriber stations belonging tothe group identified by the GROUP_ID are not necessarily assigned thesame slot on the paging channel. Consequently, a method enablingefficient method for delivering the multicast call initiationinformation is required.

[0163] In one embodiment, upon receiving the notification, thesubscriber stations are required to monitor the paging channel in anon-slotted mode; consequently, the MCAM may be sent in any pagingchannel slot.

[0164] In another embodiment, the MCAM is sent on a slot using the samemethod employed for determining a slot to send a multicast-addressednotification.

[0165] In another embodiment, the common overhead message or the commonpage message indicates the paging channel slot number, which thesubscriber stations are required to monitor for the MCAM.

[0166] In another embodiment, the MCAM is sent on each of the slotsmonitored by the subscriber stations.

[0167] It will be understood by one of ordinary skills in the art, thatthe embodiments described were treated separately for tutorial purposesonly. A communication system will use an embodiment appropriate for amulticast service. The selection of the embodiment may be specifiede.g., in the notification.

[0168] Once the subscriber station processes the message, the subscriberstation(s) interested start to monitor the assigned channel to receivemulticast service traffic.

[0169] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 16. At an instant t₁, a sector Sreceives an identity of the subscriber stations MS_1 and MS_2 GROUP_IDx,comprising a group with an identifier GROUP_IDx, for which a multicastcall is to start. Alternatively, the sector S receives a groupidentifier GROUP_IDx. The information may be provided by another entityof the communication system, e.g., a base station controller, a PSTN, asource of information (not shown), an other entities. The sector S thendetermines the identity of the subscriber stations MS_1 and MS_2, e.g.,by querying a database. The sector S then creates an individual MCPcontaining the identifier GROUP_IDx for each subscriber station MS_1 andMS_2, and includes the MCP into a page message, e.g. a general pagemessage (GPM).

[0170] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx). Subscriber station MS_1 receives theGPM(GROUP_IDx), and sends a response at time t₃.

[0171] At time t₄, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx). Subscriber stationMS_2 receives the GPM(GROUP_IDx) and sends a response at time t₅.

[0172] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign sharedchannel. The sector S waits until time t₆ for the paging slot monitoredby the subscriber station MS_1, and then conveys the individualICAM(Channel Assignment Information) to the subscriber station MS_1. Thesubscriber station MS_1 processes the ICAM and takes an appropriateaction, e.g., tunes to and starts monitoring the physical channel onwhich the identified multicast call is being transmitted.

[0173] Similarly, the sector S waits until time t₇ for the paging slotmonitored by the subscriber station MS_2, and then conveys theindividual ICAM(Channel Assignment Information) subscriber station MS_2.The subscriber station MS_2 processes the ICAM and takes an appropriateaction, e.g., tunes to and starts monitoring the physical channel onwhich the identified multicast call is being transmitted.

[0174] At time t₈ the content of the multicast service starts to betransmitted on the traffic channel (Traffic for Group_IDx).

[0175] In another embodiment, if the entity decides to assign a sharedchannel, the access network sends an Individual Channel AssignmentMessage (ICAM), containing information for the shared multicast servicetraffic channel to each responding member subscriber station. In thecontext of a communication system in accordance with the IS-2000standard, the ICAM can comprise, e.g., an Extended Channel AssignmentMessage.

[0176] Such an individual assignment is possible because, although theaccess network did not necessarily know the identities of the individualsubscriber station when sending the notification, upon receiving theresponses from subscriber stations the identities were revealed.

[0177] It is noted that because the shared multicast service trafficchannel is assigned individually as in a point-to-point call, any methodknown for a point-to-point traffic channel assignment can be used.Consequently, the issue of when to send the ICAM for each subscriberstation is not present because the access network knows when each of theinterested subscriber stations will be monitoring the paging channel.

[0178] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 17. At an instant t₁, a sector Sreceives an identity of the subscriber stations MS_1 and MS_2 GROUP_IDx,comprising a group with an identifier GROUP_IDx, for which a multicastcall is to start. Alternatively, the sector S receives a groupidentifier GROUP_IDx. The information may be provided by another entityof the communication system, e.g., a base station controller, a PSTN, asource of information (not shown), an other entities. The sector S thendetermines the identity of the subscriber stations MS_1 and MS_2, e.g.,by querying a database. The sector S then creates an individual MCPcontaining the identifier GROUP_IDx for each subscriber station MS_1 andMS_2, and includes the MCP into a page message, e.g. a general pagemessage (GPM).

[0179] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx). Subscriber station MS_1 receives theGPM(GROUP_IDx), and sends a response at time t₃.

[0180] At time t₄, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx). Subscriber stationMS_2 receives the GPM(GROUP_IDx) and sends a response at time t₅.

[0181] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign sharedchannels. The sector S determines the method of sending the individualchannel assignment message, e.g., the ICAM, to each subscriber stationMS_1 and MS_2, and sends the ICAMs containing information for the sharedmulticast service traffic channel ICAM(Channel Assignment Information)at time t₆, respective t₇. The subscriber stations MS_1 and MS_2 processthe ICAMs and take an appropriate action, e.g., tune to and startmonitoring the physical channel on which the identified multicast callis being transmitted at time t₇. At time t₇ the content of the multicastservice starts to be transmitted on the traffic channel (Traffic forGroup_IDx).

[0182] In another embodiment, if the entity decides to assign adedicated channels, the access network sends a common channel assignmentmessage, Multicast Channel Assignment Message (MCAM), containinginformation for the dedicated multicast service traffic channel. Thus,the MCAM uses a multicast address to assign the shared channel to theinterested subscriber stations.

[0183] As has been explained above, the subscriber stations belonging tothe group identified by the GROUP_ID are not necessarily assigned thesame slot on the paging channel. Consequently, a method enablingefficient method for delivering the multicast call initiationinformation is required.

[0184] In one embodiment, upon receiving the notification, thesubscriber stations are required to monitor the paging channel in anon-slotted mode; consequently, the MCAM may be sent in any pagingchannel slot.

[0185] In another embodiment, the MCAM is sent on a slot using the samemethod employed for determining a slot to send a multicast-addressednotification.

[0186] In another embodiment, the common overhead message or the commonpage message indicates the paging channel slot number, which thesubscriber stations are required to monitor for the MCAM.

[0187] In another embodiment, the MCAM is sent on each of the slotsmonitored by the subscriber stations.

[0188] It will be understood by one of ordinary skills in the art, thatthe embodiments described were treated separately for tutorial purposesonly. A communication system will use an embodiment appropriate for amulticast service. The selection of the embodiment may be specifiede.g., in the notification.

[0189] Once the subscriber station processes the message, the subscriberstation(s) interested start to monitor the assigned channel to receivemulticast service traffic.

[0190] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 18. At an instant t₁, a sector Sreceives an identity of the subscriber stations MS_1 and MS_2 GROUP_IDx,comprising a group with an identifier GROUP_IDx, for which a multicastcall is to start. Alternatively, the sector S receives a groupidentifier GROUP_IDx. The information may be provided by another entityof the communication system, e.g., a base station controller, a PSTN, asource of information (not shown), an other entities. The sector S thendetermines the identity of the subscriber stations MS_1 and MS_2, e.g.,by querying a database. The sector S then creates an individual MCPcontaining the identifier GROUP_IDx for each subscriber station MS_1 andMS_2, and includes the MCP into a page message, e.g. a general pagemessage (GPM).

[0191] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx). Subscriber station MS_1 receives theGPM(GROUP_IDx), and sends a response at time t₃.

[0192] At time t₄, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx). Subscriber stationMS_2 receives the GPM(GROUP_IDx) and sends a response at time t₅.

[0193] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign dedicatedchannels. The sector S determines the method of sending the commonchannel assignment message, e.g., the MCAM, and sends the MCAMcontaining information for the dedicated multicast service trafficchannel MCAM(Channel Assignment Information for MS_1, Channel AssignmentInformation for MS_2) at time t₆. The subscriber station MS_1 and MS_2process the MCAM and take an appropriate action, e.g., tune to and startmonitoring the dedicated physical channels Traffic for MS_1 respectiveTraffic for MS_2, on which the identified multicast call is beingtransmitted at time t₇ respective t₈.

[0194] In another embodiment, if the entity decides to assign dedicatedchannels, the access network sends an individual channel assignmentmessage (Individual Channel Assignment Message—ICAM), containinginformation for the shared multicast service traffic channel to eachresponding member subscriber station. In the context of a communicationsystem in accordance with the IS-2000 standard, the ICAM can comprise,e.g., the Extended Channel Assignment Message could be used.

[0195] It is noted that because the shared multicast service trafficchannel is assigned individually as in a point-to-point call, any methodknown for a point-to-point traffic channel assignment can be used.Consequently, the issue of when to send the ICAM for each subscriberstation is not present because the access network knows when each of theinterested subscriber stations will be monitoring the paging channel.

[0196] An example of message flow in accordance with the above-describedembodiment is illustrated in FIG. 19. At an instant t₁, a sector Sreceives an identity of the subscriber stations MS_1 and MS_2GROUP_ID_x, comprising a group with an identifier GROUP_IDx, for which amulticast call is to start. Alternatively, the sector S receives a groupidentifier GROUP_IDx. The information may be provided by another entityof the communication system, e.g., a base station controller, a PSTN, asource of information (not shown), an other entities. The sector S thendetermines the identity of the subscriber stations MS_1 and MS_2, e.g.,by querying a database. The sector S then creates an individual MCPcontaining the identifier GROUP_IDx for each subscriber station MS_1 andMS_2, and includes the MCP into a page message, e.g. a general pagemessage (GPM).

[0197] The sector S then determines the slots on a paging channelmonitored by the member subscriber stations MS_1 and MS_2. At time t₂,in a slot monitored by the member subscriber stations MS_1, the sector Stransmits the GPM(MCP:GROUP_IDx). Subscriber station MS_1 receives theGPM(GROUP_IDx), and sends a response at time t₃.

[0198] At time t₄, in a slot monitored by the member subscriber stationsMS_2, the sector S transmits the GPM(MCP:GROUP_IDx). Subscriber stationMS_2 receives the GPM(GROUP_IDx) and sends a response at time t₅.

[0199] Upon receiving the responses, the entity of the access networkresponsible for the channel assignment determines to assign dedicatedchannel. The sector S waits until time t₆ for the paging slot monitoredby the subscriber station MS_1, and then conveys the individualICAM(Channel Assignment Information for MS_1) to the subscriber stationMS_1. The subscriber station MS_1 processes the ICAM and takes anappropriate action, e.g., tunes to and starts monitoring the physicalchannel on which the identified multicast call for the subscriberstation MS_1 is being transmitted (Traffic for MS_1) at time t₇.

[0200] Similarly, the sector S waits until time t₈ for the paging slotmonitored by the subscriber station MS_2, and then conveys theindividual ICAM(Channel Assignment Information for MS_2) to thesubscriber station MS_2. The subscriber station MS_2 processes the ICAMand takes an appropriate action, e.g., tunes to and starts monitoringthe physical channel on which the identified multicast call for thesubscriber station MS_2 is being transmitted (Traffic for MS_2) at timet₉.

[0201] It will be understood by one of ordinary skills in the art thatthe above-described embodiments were treated separately for tutorialpurposes only. A communication system will use any embodimentappropriate for a multicast service. For example, for a multicast callto be delivered to a multicast group whose members are in a coveragearea of different sectors, each sector may use different embodiment.Thus, one sector may use multicast notification, require a response, andassign dedicated channel. Another sector may use individualnotification, require a response, and assign shared channel. Yet anothersector may use multicast notification, require a response, and assign ashared channel to some subscriber stations and a dedicated channel toremaining subscriber stations.

[0202] One skilled in the art will appreciate that although theflowchart diagrams are drawn in sequential order for comprehension,certain steps can be carried out in parallel in an actualimplementation.

[0203] Those of skill in the art would understand that information andsignals may be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0204] Those of skill would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

[0205] The various illustrative logical blocks, modules, and circuitsdescribed in connection with the embodiments disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

[0206] The steps of a method or algorithm described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

[0207] The previous description of the disclosed embodiments is providedto enable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

[0208] A portion of the disclosure of this patent document containsmaterial which is subject to copyright protection. The copyright ownerhas no objection to the facsimile reproduction by anyone of the patentdocument or the patent disclosure, as it appears in the Patent andTrademark Office patent file or records, but otherwise reserves allcopyright rights whatsoever.

What is claimed is:
 1. A method for a multicast service notification ina communication system, comprising: determining a multicast groupidentifier; and including the multicast group identifier in at least oneperiodically repeated message on a first channel.
 2. The method asclaimed in claim 1 wherein said determining a multicast group identifiercomprises: receiving the multicast group identifier from an entity ofthe communication system.
 3. The method as claimed in claim 1 whereinsaid determining a multicast group identifier comprises: receiving anidentity of subscriber stations belonging to a multicast group; anddetermining the multicast group identifier in accordance with theidentity of the subscriber stations.
 4. The method as claimed in claim1, further comprising: receiving an end indicator for a multicastservice for subscriber stations identified by the multicast groupidentifier; and removing the multicast group identifier from theperiodically repeated message on the first channel if the multicastgroup identifier is included in every periodically repeated message. 5.The method as claimed in claim 1, further comprising: receiving an endindicator for a multicast service for subscriber stations identified bythe multicast group identifier; and including the end indicator into asignal conveyed over a second channel, if the multicast group identifieris not included in every periodically repeated message.
 6. The method asclaimed in claim 5, wherein said including the end indicator into asignal conveyed over a second channel comprises: including the endindicator into a signal conveyed over a channel conveying the multicastservice.
 7. A method for a multicast service notification of asubscriber station in a communication system, comprising: monitoring aperiodically repeated message on a channel; and decoding theperiodically repeated message to determine if a multicast servicenotification was included in the periodically repeated message.
 8. Themethod as claimed in claim 7, further comprising: receiving a channelconveying the multicast service.
 9. The method as claimed in claim 8,further comprising: receiving an end indicator over the channelconveying the multicast service; and discontinuing reception of thechannel conveying the multicast service.
 10. The method as claimed inclaim 8, further comprising: receiving an end indicator over a secondchannel; and discontinuing reception of the channel conveying themulticast service.
 11. An apparatus for a multicast service notificationin a communication system, comprising: a processor; and a storage mediumcoupled to the processor and containing a set of instructions executableby the processor to: determine a multicast group identifier; and includethe multicast group identifier in at least one periodically repeatedmessage on a first channel.
 12. The apparatus as claimed in claim 11wherein said processor determines a multicast group identifier byprocessing a set of instructions to: receive the multicast groupidentifier from an entity of the communication system.
 13. The apparatusas claimed in claim 11 wherein said processor determines a multicastgroup identifier by processing a set of instructions to: receive anidentity of subscriber stations belonging to a multicast group; anddetermine the multicast group identifier in accordance with the identityof the subscriber stations.
 14. The apparatus as claimed in claim 11wherein said processor is further configured to: receive an endindicator for a multicast service for subscriber stations identified bythe multicast group identifier; and remove the multicast groupidentifier from the periodically repeated message on the first channelif the multicast group identifier is included in every periodicallyrepeated message.
 15. The apparatus as claimed in claim 11 wherein saidprocessor is further configured to: receive an end indicator for amulticast service for subscriber stations identified by the multicastgroup identifier; and include the end indicator into a signal conveyedover a second channel, if the multicast group identifier is not includedin every periodically repeated message.
 16. The apparatus as claimed inclaim 15, wherein said processor includes the end indicator into asignal conveyed over a second channel by processing a set ofinstructions to: include the end indicator into a signal conveyed over achannel conveying the multicast service.
 17. The apparatus as claimed inclaim 17, wherein said processor and said storage medium are disposed ina base station.
 18. The apparatus as claimed in claim 17 wherein themulticast group identifier is received from an entity of thecommunication system different from the base station.
 19. A apparatusfor a multicast service notification in a communication system,comprising: a subscriber station configured to: monitor a periodicallyrepeated message on a channel; and decode the periodically repeatedmessage to determine if a multicast service notification was included inthe periodically repeated message.
 20. The apparatus as claimed in claim19 wherein said subscriber station is further configured to: receive achannel conveying the multicast service.
 21. The apparatus as claimed inclaim 20 wherein said subscriber station is further configured to:receive an end indicator over the channel conveying the multicastservice; and discontinue reception of the channel conveying themulticast service
 22. The apparatus as claimed in claim 19 wherein saidsubscriber station is further configured to: receive an end indicatorover a second channel; and discontinue reception of the channelconveying the multicast service
 23. A method for a multicast servicenotification in a communication system, comprising: determining identityof subscriber stations belonging to a multicast group; determining aslot of a channel in accordance with the identity of a subscriberstation; and transmitting a multicast service notification in the sloton a channel.
 24. The method as claimed in claim 23 wherein saiddetermining identity of subscriber station belonging to a multicastgroup comprises: receiving the identity of subscriber station from anentity of the communication system.
 25. The method as claimed in claim23 wherein said determining identity of subscriber station belonging toa multicast group comprises: receiving a multicast group identifier froman entity of the communication system; and determining identity ofsubscriber station in accordance with the multicast group identifier.26. A method for a multicast service notification in a communicationsystem, comprising: monitoring a slot of a channel; and decoding amessage conveyed in the slot to determine if a multicast servicenotification was included in the message.
 27. The method as claimed inclaim 26 wherein monitoring a slot of a channel comprises: determiningthe slot in accordance with the identity of a subscriber station.
 28. Anapparatus for a multicast service notification in a communicationsystem, comprising: a processor; and a storage medium coupled to theprocessor and containing a set of instructions executable by theprocessor to: determine identity of subscriber stations belonging to amulticast group; determine a slot of a channel, the slot correspondingto the identity of a subscriber station; and transmit a multicastservice notification in the slot on a channel.
 29. An apparatus for amulticast service notification of a subscriber station in acommunication system, comprising: a subscriber station configured to:monitoring a slot of a channel; and decoding a message conveyed in theslot to determine if a multicast service notification was included inthe message.
 30. A method for a multicast service notification in acommunication system, comprising: including an indicator into apre-determined slot on a first channel; and including a multicastservice notification into a message conveyed in a slot on a secondchannel, the slot corresponding to the pre-determined slot on the firstchannel, if a multicast service notification was indicated by theindicator.
 31. The method as claimed in claim 30 wherein said includingthe indicator into a pre-determined slot comprises: determining abroadcast paging cycle; and including the indicator into an n-th slot ofeach broadcast paging cycle.
 32. The method as claimed in claim 31wherein said including the indicator into an n-th slot of each broadcastpaging cycle comprises: including the indicator into the first slot ofeach broadcast paging cycle.
 33. The method as claimed in claim 30wherein said including a multicast service notification into a messageconveyed in a slot on a second channel comprises: including themulticast service notification in the slot on the second channel, theslot being offset from the pre-determined slot on the first channel by apre-determined interval.
 34. A method for a multicast servicenotification of a subscriber station in a communication system,comprising: decoding an indicator from a pre-determined slot on a firstchannel; and decoding a multicast service notification in a slot on asecond channel, the slot corresponding to the pre-determined slot on thefirst channel, if a multicast service notification was indicated by theindicator.
 35. The method as claimed in claim 34 wherein decoding anindicator from a pre-determined slot on a first channel comprises:determining a broadcast paging cycle; and decoding the indicator in ann-th slot of each broadcast paging cycle.
 36. The method as claimed inclaim 35 wherein said decoding an indicator in an n-th slot of eachbroadcast paging cycle comprises: decoding the indicator in a first slotof each broadcast paging cycle
 37. The method as claimed in claim 34wherein said decoding a multicast service notification in a slot on asecond channel comprises: decoding the multicast service notification inthe slot on the second channel, the slot being offset from thepre-determined slot on the first channel by a pre-determined interval.38. An apparatus for a multicast service notification in a communicationsystem, comprising: a processor; and a storage medium coupled to theprocessor and containing a set of instructions executable by theprocessor to: include an indicator into a pre-determined slot on a firstchannel; and include a multicast service notification into a messageconveyed in a slot on a second channel, the slot corresponding to thepre-determined slot on the first channel, if a multicast servicenotification was indicated by the indicator.
 39. The apparatus asclaimed in claim 38 wherein said processor includes an indicator into apre-determined slot by executing a set of instructions to: determine abroadcast paging cycle; and include the indicator into an n-th slot ofeach broadcast paging cycle.
 40. The apparatus as claimed in claim 39wherein said processor includes the indicator into an n-th slot of eachbroadcast paging cycle by executing a set of instructions to: includethe indicator into the first slot of each broadcast paging cycle. 41.The apparatus as claimed in claim 38 wherein said processor includes amulticast service notification into a message conveyed in a slot on asecond channel by executing a set of instructions to include themulticast service notification in the slot on the second channel, theslot being offset from the pre-determined slot on the first channel by apre-determined interval.
 42. The apparatus as claimed in claim 38wherein said processor and said storage medium are disposed in a basestation.
 43. A apparatus for a multicast service notification of asubscriber station in a communication system, comprising: a subscriberstation configured to: decode an indicator from a pre-determined slot ona first channel; and decode a multicast service notification in a sloton a second channel, the slot corresponding to the pre-determined sloton the first channel, if a multicast service notification was indicatedby the indicator.
 44. The apparatus as claimed in claim 43 wherein saidsubscriber station decodes an indicator from a pre-determined slot on afirst channel by being configured to: determine a broadcast pagingcycle; and decode the indicator in an n-th slot of each broadcast pagingcycle.
 45. The apparatus as claimed in claim 44 wherein said subscriberstation decodes the indicator in an n-th slot of each broadcast pagingcycle by being configured to: decode the indicator in a first slot ofeach broadcast paging cycle
 46. The apparatus as claimed in claim 43wherein said subscriber station decodes a multicast service notificationin a slot on a second channel by being configured to: decode themulticast service notification in the slot on the second channel, theslot being offset from the pre-determined slot on the first channel by apre-determined interval.
 47. A method for a multicast servicenotification in a communication system, comprising: including anindicator into a first slot on a first channel; and including amulticast service notification into a message conveyed in a second sloton a second channel, the second slot corresponding to the first slot, ifa multicast service notification was indicated by the indicator.
 48. Themethod as claimed in claim 47 wherein said including an indicator into afirst slot comprises: determining a multicast paging cycle; anddetermining the first slot in accordance with the multicast paging cycleand a multicast group identifier.
 49. The method as claimed in claim 48wherein said determining the first slot in accordance with the multicastpaging cycle and a multicast group identifier comprises: inputting themulticast paging cycle and the multicast group identifier into a hashingfunction; and setting the first slot to a value outputted by the hashingfunction.
 50. The method as claimed in claim 47 wherein said including amulticast service notification into a message conveyed in a second sloton a second channel comprises: including the multicast servicenotification into the message conveyed in the second slot on the secondchannel, the second slot being offset from the first slot by apre-determined interval.
 51. The method as claimed in claim 50 whereinsaid second slot being offset from the first slot by a pre-determinedinterval comprises: second slot being offset from the first slot by 100milliseconds.
 52. A method for a multicast service notification of asubscriber station in a communication system, comprising: decoding anindicator from a first slot on a first channel; and decoding a multicastservice notification in a second slot on a second channel, the secondslot corresponding to the first slot, if a multicast servicenotification was indicated by the indicator.
 53. The method as claimedin claim 52 wherein said decoding an indicator from a first slot on afirst channel comprises: determining a multicast paging cycle; anddetermining the first slot in accordance with the multicast paging cycleand a multicast group identifier.
 54. The method as claimed in claim 53wherein said determining the first slot in accordance with the multicastpaging cycle and a multicast group identifier comprises: inputting themulticast paging cycle and a multicast group identifier into a hashingfunction; and setting the first slot to a value outputted by the hashingfunction.
 55. The method as claimed in claim 52 wherein said decoding amulticast service notification in a second slot on a second channel, thesecond slot corresponding to the first slot comprises: decoding themulticast service notification in the second slot, the second slot beingoffset from the first slot by a pre-determined interval.
 56. The methodas claimed in claim 55 wherein said second slot being offset from thefirst slot by a pre-determined interval comprises: second slot beingoffset from the first slot by 100 miliseconds.
 57. An apparatus for amulticast service notification in a communication system, comprising: aprocessor; and a storage medium coupled to the processor and containinga set of instructions executable by the processor to: include anindicator into a first slot on a first channel; and include a multicastservice notification into a message conveyed in a second slot on asecond channel, the second slot corresponding to the first slot, if amulticast service notification was indicated by the indicator.
 58. Theapparatus as claimed in claim 57 wherein said processor includes anindicator into a first slot by executing a set of instructions to:determine a multicast paging cycle; and determine the first slot inaccordance with the multicast paging cycle and a multicast groupidentifier.
 59. The apparatus as claimed in claim 58 wherein saidprocessor determines the first slot in accordance with the multicastpaging cycle and a multicast group identifier by executing a set ofinstructions to: input the multicast paging cycle and a multicast groupidentifier into a hashing function; and set the first slot to a valueoutputted by the hashing function.
 60. The apparatus as claimed in claim57 wherein said processor includes a multicast service notification intoa message conveyed in a second slot on a second channel by executing aset of instructions to: include a multicast service notification into amessage conveyed in a second slot on a second channel, the second slotbeing offset from the first slot by a pre-determined interval.
 61. Theapparatus as claimed in claim 60 wherein said second slot is offset fromthe first slot by 100 miliseconds.
 62. The apparatus as claimed in claim57, wherein said processor and said storage medium are disposed in abase station.
 63. A apparatus for a multicast service notification of asubscriber station in a communication system, comprising: a subscriberstation configured to: decode an indicator from a first slot on a firstchannel; and decode a multicast service notification in a second slot ona second channel, the second slot corresponding to the first slot, if amulticast service notification was indicated by the indicator.
 64. Theapparatus as claimed in claim 63 wherein said subscriber station decodesan indicator from a first slot on a first channel by being configuredto: determine a multicast paging cycle; and determine the first slot inaccordance with the multicast paging cycle and a multicast groupidentifier.
 65. The apparatus as claimed in claim 64 wherein saidsubscriber station determines the first slot in accordance with themulticast paging cycle and a multicast group identifier by beingconfigured to: input the multicast paging cycle and a multicast groupidentifier into a hashing function; and set the first slot to a valueoutputted by the hashing function.
 66. The apparatus as claimed in claim63 wherein said subscriber station decodes a multicast servicenotification in a second slot on a second channel, the second slotcorresponding to the first slot by being configured to: decode amulticast service notification in a second slot, the second slot beingoffset from the first slot by a pre-determined interval.
 67. Theapparatus as claimed in claim 66 wherein said second slot being offsetfrom the first slot by a pre-determined interval comprises: second slotbeing offset from the first slot by 100 miliseconds.
 68. A method for amulticast service notification in a communication system, comprising:establishing a link layer protocol between a subscriber stationbelonging to a multicast group and an entity of an access network; andconveying the multicast service notification over the link layerprotocol.
 69. The method as claimed in claim 68 wherein saidestablishing a link layer protocol comprises: determining identity ofsubscriber stations belonging to the multicast group; determining a slotof a channel in accordance with the identity of a subscriber station;and including a link layer protocol establishment request in the slot onthe channel.
 70. The method as claimed in claim 69 wherein saiddetermining identity of subscriber stations belonging to a multicastgroup comprises: receiving the identity of subscriber stations from anentity of the communication system.
 71. The method as claimed in claim69 wherein said determining identity of subscriber stations belonging toa multicast group comprises: receiving a multicast group identifier froman entity of the communication system; and determining identity ofsubscriber station in accordance with the multicast group identifier.72. A method for a multicast service notification in a communicationsystem, comprising: establishing a link layer protocol between asubscriber station belonging to a multicast group and an entity of theaccess network; and receiving, at the subscriber station belonging tothe multicast group, the multicast service notification over the linklayer protocol.
 73. The method claimed in claim 72 wherein saidestablishing a link layer protocol comprises: monitoring, by thesubscriber station, a slot of a channel; and establishing a link layerprotocol between the subscriber station and the entity of the accessnetwork if a message conveyed in the slot comprises a link layerprotocol establishment request.
 74. The method as claimed in claim 68wherein said establishing a link layer protocol comprises: including anindicator into a pre-determined slot on a first channel; and including alink layer protocol establishment request into a message conveyed in aslot on a second channel, the slot corresponding to the pre-determinedslot on the first channel, if a multicast service notification wasindicated by the indicator.
 75. The method as claimed in claim 74wherein said including an indicator into a pre-determined slotcomprises: determining a broadcast paging cycle; and including anindicator into an n-th slot of each broadcast paging cycle.
 76. Themethod as claimed in claim 75 wherein including an indicator into ann-th slot of each broadcast paging cycle comprises: including theindicator into a first slot of each broadcast paging cycle.
 77. Themethod as claimed in claim 74 wherein said including a link layerprotocol establishment request in a slot on a second channel comprises:including the link layer protocol establishment request in the slot onthe second channel, the slot being offset from the pre-determined sloton the first channel by a pre-determined interval.
 78. The method asclaimed in claim 72 wherein said establishing a link layer protocolcomprises: decoding an indicator from a pre-determined slot on a firstchannel; and decoding a link layer protocol establishment request in aslot on a second channel, the slot corresponding to the pre-determinedslot on the first channel, if a multicast service notification wasindicated by the indicator.
 79. The method as claimed in claim 78wherein decoding an indicator from a pre-determined slot on a firstchannel comprises: determining a broadcast paging cycle; and decoding anindicator in an n-th slot of each broadcast paging cycle.
 80. The methodas claimed in claim 79 wherein said decoding an indicator in an n-thslot of each broadcast paging cycle comprises: decoding an indicator ina first slot of each broadcast paging cycle
 81. The method as claimed inclaim 78 wherein said decoding a link layer protocol establishmentrequest in a slot on a second channel comprises: decoding a multicastservice notification in a slot on a second channel, the slot beingoffset from the pre-determined slot on the first channel by apre-determined interval.
 82. The method as claimed in claim 68 whereinsaid establishing a link layer protocol comprises: including anindicator into a first slot on a first channel; and including a linklayer protocol establishment request into a message conveyed in a secondslot on a second channel, the second slot corresponding to the firstslot, if a multicast service notification was indicated by theindicator.
 83. The method as claimed in claim 82 wherein said includingan indicator into a first slot comprises: determining a multicast pagingcycle; and determining the first slot in accordance with the multicastpaging cycle and a multicast group identifier.
 84. The method as claimedin claim 83 wherein said determining the first slot in accordance withthe multicast paging cycle and a multicast group identifier comprises:inputting the multicast paging cycle and a multicast group identifierinto a hashing function; and setting the first slot to a value outputtedby the hashing function.
 85. The method as claimed in claim 82 whereinsaid including a link layer protocol establishment request into amessage conveyed in a second slot on a second channel comprises:including a link layer protocol establishment request into a messageconveyed in a second slot on a second channel, the second slot beingoffset from the first slot by a pre-determined interval.
 86. The methodas claimed in claim 72 wherein said establishing a link layer protocolcomprises: decoding an indicator from a first slot on a first channel;and decoding a link layer protocol establishment request in a secondslot on a second channel, the second slot corresponding to the firstslot, if a multicast service notification was indicated by theindicator.
 87. The method as claimed in claim 86 wherein said decodingan indicator from a first slot on a first channel comprises: determininga multicast paging cycle; and determining the first slot in accordancewith the multicast paging cycle and a multicast group identifier. 88.The method as claimed in claim 86 wherein said decoding a link layerprotocol establishment request in a second slot on a second channel, thesecond slot corresponding to the first slot comprises: decoding amulticast service notification in a second slot, the second slot beingoffset from the first slot by a pre-determined interval.
 89. Anapparatus for a multicast service notification in a communicationsystem, comprising: a processor; and a storage medium coupled to theprocessor and containing a set of instructions executable by theprocessor to: establish a link layer protocol between a subscriberstation belonging to a multicast group and an entity of the accessnetwork; and convey the multicast service notification over the linklayer protocol.
 90. The apparatus as claimed in claim 89 wherein saidprocessor establishes a link layer protocol by executing a set ofinstructions to: determine an identity of subscriber stations belongingto the multicast group; determine a slot of a channel, the slotcorresponding to the identity of a subscriber station; and include alink layer protocol establishment request in the slot on a channel. 91.The apparatus as claimed in claim 90 wherein said processor determinesidentity of subscriber stations belonging to a multicast group byexecuting a set of instructions to: receive the identity of subscriberstations from an entity of the communication system.
 92. The apparatusas claimed in claim 90 wherein said processor determines identity ofsubscriber stations belonging to a multicast group by executing a set ofinstructions to: receive a multicast group identifier from an entity ofthe communication system; and determine the identity of subscriberstation in accordance with the multicast group identifier.
 93. Aapparatus for a multicast service notification in a communicationsystem, comprising: a subscriber station configured to: establish a linklayer protocol between a subscriber station belonging to a multicastgroup and an entity of an access network; and receive the multicastservice notification over the link layer protocol.
 94. The apparatusclaimed in claim 93 wherein said subscriber station establishes linklayer protocol by being configured to: monitor a slot of a channel; andestablish a link layer protocol between the subscriber station and theentity of the access network if a message conveyed in the slot comprisesa link layer protocol establishment request.
 95. The apparatus asclaimed in claim 89 wherein said processor establishes a link layerprotocol by executing a set of instruction to: include an indicator intoa pre-determined slot on a first channel; and include a link layerprotocol establishment request into a message conveyed in a slot on asecond channel, the slot corresponding to the pre-determined slot on thefirst channel, if a multicast service notification was indicated by theindicator.
 96. The apparatus as claimed in claim 95 wherein saidprocessor includes an indicator into a pre-determined slot by executinga set of instructions to: determine a broadcast paging cycle; andinclude an indicator into an n-th slot of each broadcast paging cycle.97. The apparatus as claimed in claim 93 wherein said processor includesan indicator into an n-th slot of each broadcast paging cycle byexecuting a set of instructions to: include an indicator into the firstslot of each broadcast paging cycle.
 98. The apparatus as claimed inclaim 95 wherein said processor includes a link layer protocolestablishment request into a message conveyed in a slot on a secondchannel by executing a set of instructions to include a multicastservice notification in a slot on a second channel, the slot beingoffset from the pre-determined slot on the first channel by apre-determined interval.
 99. The apparatus claimed in claim 93 whereinsaid subscriber station establishes link layer protocol by beingconfigured to: decode an indicator from a pre-determined slot on a firstchannel; and decode a link layer protocol establishment request in aslot on a second channel, the slot corresponding to the pre-determinedslot on the first channel, if a link layer protocol establishmentrequest was indicated by the indicator.
 100. The apparatus as claimed inclaim 99 wherein said subscriber station decodes an indicator from apre-determined slot on a first channel by being configured to: determinea broadcast paging cycle; and decode an indicator in an n-th slot ofeach broadcast paging cycle.
 101. The apparatus as claimed in claim 100wherein said subscriber station decodes an indicator in an n-th slot ofeach broadcast paging cycle by being configured to: decode an indicatorin a first slot of each broadcast paging cycle
 102. The apparatus asclaimed in claim 99 wherein said subscriber station decodes a link layerprotocol establishment request in a slot on a second channel by beingconfigured to: decode a link layer protocol establishment request in aslot on a second channel, the slot being offset from the pre-determinedslot on the first channel by a pre-determined interval.
 103. Theapparatus as claimed in claim 89 wherein said processor establishes alink layer protocol by executing a set of instruction to: include anindicator into a first slot on a first channel; and include a link layerprotocol establishment request into a message conveyed in a second sloton a second channel, the second slot corresponding to the first slot, ifa link layer protocol establishment request was indicated by theindicator.
 104. The apparatus as claimed in claim 103 wherein saidprocessor includes an indicator into a first slot by executing a set ofinstructions to: determine a multicast paging cycle; and determine thefirst slot in accordance with the multicast paging cycle and a multicastgroup identifier.
 105. The apparatus as claimed in claim 104 whereinsaid processor determines the first slot in accordance with themulticast paging cycle and a multicast group identifier by executing aset of instructions to: input the multicast paging cycle and a multicastgroup identifier into a hashing function; and set the first slot to avalue outputted by the hashing function.
 106. The apparatus as claimedin claim 103 wherein said processor includes a link layer protocolestablishment request into a message conveyed in a second slot on asecond channel by executing a set of instructions to: include a linklayer protocol establishment request into a message conveyed in a secondslot on a second channel, the second slot being offset from the firstslot by a pre-determined interval.
 107. The apparatus as claimed inclaim 106 wherein said second slot is offset from the first slot by 100miliseconds.
 108. The apparatus as claimed in claim 99, wherein saidprocessor and said storage medium are disposed in a base station. 109.The apparatus claimed in claim 93 wherein said subscriber stationestablishes link layer protocol by being configured to: decode anindicator from a first slot on a first channel; and decode a link layerprotocol establishment request in a second slot on a second channel, thesecond slot corresponding to the first slot, if a link layer protocolestablishment request was indicated by the indicator.
 110. The apparatusas claimed in claim 109 wherein said subscriber station decodes anindicator from a first slot on a first channel by being configured to:determine a multicast paging cycle; and determine the first slot inaccordance with the multicast paging cycle and a multicast groupidentifier.
 111. The apparatus as claimed in claim 110 wherein saidsubscriber station determines the first slot in accordance with themulticast paging cycle and a multicast group identifier by beingconfigured to: input the multicast paging cycle and a multicast groupidentifier into a hashing function; and set the first slot to a valueoutputted by the hashing function.
 112. The apparatus as claimed inclaim 109 wherein said subscriber station decodes a link layer protocolestablishment request in a second slot on a second channel, the secondslot corresponding to the first slot by being configured to: decode alink layer protocol establishment request in a second slot, the secondslot being offset from the first slot by a pre-determined interval. 113.The apparatus as claimed in claim 112 wherein said second slot beingoffset from the first slot by a pre-determined interval comprises:second slot being offset from the first slot by 100 miliseconds.